The invention relates to industrial cargo webbing slings used with hoist equipment to lift cargo and articles.
Braided wire, chains, miscellaneous cables, and webbing slings have been utilized with industrial hoist equipment. The present invention relates to webbing slings which have become increasingly popular. Typically, webbing slings are made from lengths of woven webbing having multiple plies. The slings are made in different strength grades depending upon the construction. The webbing is woven from suitable synthetic yarns like nylon or polyester. The webbing is fabricated into a sling for the purpose of hoisting, lifting and general material handling. Webbing with soft eyes is shown in U.S. Pat. Nos. 2,903,291, 3,592,502, 3,776,585, and 4,025,100. Typical weave patterns are shown in the patents for webbing. The problems of abrading and cutting of the selvage edge occur with webbing slings. Most of the load is concentrated at the selvage edge of the webbing. For example, in lifting railroad cargo such as large I-beams, the edges of the webbing encounter the sharp edges of the metal I-beams. When the edge is cut, the webbing sling must be taken out of service. Often the material portion of the webbing is still strong and in tact.
In the past, webbing slings have been treated with different substances such as latex for increased abrasion resistance. Also, web pads which fit over the webbing sling have been provided to reduce abrasion or cutting of the edges. The web pads typically include a length of chrome leather, or webbing folded over the edges of the sling to afford protection to both sides of both edges. Sling life may be prolonged by treating the webbing or using web pads. However, latex treatment offers limited abrasion resistance. Web pads may easily become moved along the length of the sling so that they are no longer in a protective position. Once the cargo or load is lifted, it is not possible to relocate the webbing. In other cases, the operator is careless or not interested in positioning the protective pad carefully. In either case, abrasion protection is lost and the sling may wear out prematurely.
U.S. Pat. No. 4,025,100 discloses weaving carpet type polypropylene yarns in the outer plies of the sling to exhibit higher abrasion resistance and provide a wear surface on each side of the sling. However, the edges contain no additional protection. The edges still wear faster than the planar side surfaces. U.S. Pat. No. 4,052,095 discloses a web sling woven from plastic strands having a laminate of elastomeric material or cured onto the load contacting surface of the sling. The elastomeric material may become embedded in the open mesh of the weave causing the portions of the webbing covered by the material to lose some of its softness and flexibility.
Accordingly, an important object of the present invention is to provide an industrial cargo sling of the webbing type having edges which effectively resist abrasion and cutting.
Another object of the invention is to provide an industrial cargo sling of the webbing type having its edges reinforced against abrasion and cutting without loss of flexibility.
Another object of the invention is to provide a webbing sling having its edges reinforced along their entire length while exhibiting uniform elongation properties at each section of the webbing.
Another object of the present invention is to provide an industrial cargo sling of the webbing type having its edges reinforced against abrasion and cutting continuously along the entire length of the sling so that abrasion resistance may be reliably provided at any load point along the length of its edge.